1. Field of the Invention
The present invention relates to semiconductor device and manufacturing method thereof, and more particularly, to a semiconductor device on semi-SOI (silicon on insulator) and a manufacturing method thereof.
2. Description of the Related Art
One important property of high performance semiconductor devices is their conductivity. It has been known that current is inversely proportional to resistance. Traditionally, resistivity of an electronic device can be reduced, and therefore, current can be increased, through increasing sectional size of semiconductor material, shortening electron channel length, increasing voltage, or reducing resistivity of semiconductor material.
In order to manufacture integrated circuits (IC) having higher integration than those of the prior art, such as memory, logic circuit and the like, many efforts have been taken to further reduce the size of field effect transistors (FET), such as metal-oxide-semiconductor field effect transistors (MOSFET) and complementary metal oxide semiconductor field effect transistors (CMOS). Through decreasing the total size of a device and lowering operation voltage while maintaining electrical properties of the device, the device can be made more compact and its performance can be improved. Furthermore, in order to optimize various electrical properties of the device, the sizes of all elements in a device must be decreased in proportion at the same time.
However, with such smaller semiconductor devices, as shown in FIG. 4, source-drain junction parasitic capacitance is becoming larger. On the other hand, channel size may become smaller correspondingly, and therefore, source to drain punch leakage is more liable to occur. Moreover, for the downsized devices, the influence of short channel effects is more notable.
Therefore, there is need for a new semiconductor device.